1. Field of the Invention
The present invention relates to the field of photoreactive or photoresponsive dyes, particularly photochromic dyes that change their absorbance characteristics in response to ambient radiation conditions. The invention also relates to the use of such photoresponsive dyes in compositions, coatings, layers and lenses, particularly ophthalmic lenses (both prescription and piano lenses).
2. Background of the Art
Conventional commercial photoreactive lenses, i.e. lenses that darken in sunlight and lighten again in the shade, are manufactured from glass and utilize the reversible formation of silver particles from dispersed silver halide salts to bring about the darkening of the lenses.
Plastic lenses have advantages over glass; principally they are lighter in weight (particularly in the case of ophthalmic lenses having high powers) and less prone to breakage. Since the above described action of dispersed silver salts does not take place in plastics matrices, attempts have been made to develop photochromic compounds which would produce the same kind of effect in plastics materials. The ideal compound for this purpose should, when absorbed or coated on a conventional plastics lens, possess the following properties i.e., a high quantum yield for coloring in the near ultra-violet, a low quantum yield for bleaching with visible light, and a fast thermal fade at ambient temperatures.
Unfortunately, these properties are also generally associated with thermal or photochemical instability so that the useful life of sunglasses incorporating such compounds would be too short for commercial feasibility.
U.S. Pat. No. 3,567,605 (Becker) describes a series of pyran derivatives, including certain benzopyrans and naphthopyrans, but not spiro-compounds, which exhibit photochromic properties. These compounds can be regarded as derivatives of chromene. Typically, the compounds undergo a colorless to yellow-orange change on irradiation by U.V. light. However, the observation of this behavior by Becker was restricted to temperatures below about −40° C. and Becker reported that the color change was reversed when the temperature was raised to a temperature in the range of −10° C. to 0° C.
Padwa et al in J. Org. Chem., vol. 40, No. 8, 1975, page 1142, examined the photochemical reactions of compounds of the kind described by Becker, identified the by-products and suggested pathways to ring-opened colored intermediates and the final non-colored phenolics. The colored forms examined by Padwa were unstable at room temperature, at which temperature he suggested that the colored quinoneallide intermediates either thermally revert to the starting material or undergo 1,4 addition of the methanol solvent to form the corresponding phenolic ether product or a 1,5-hydrogen shift in acetone to form the corresponding phenol. However, Padwa does not suggest ways in which the stability of the compounds he examined might be improved nor any modification which might be made to the structure of known pyran compounds in order to induce photoreactive behavior in a plastics lens.
The required properties of a photochromic compound for sunglasses application are outlined above and compounds which possess these properties have been termed “heliochromic” compounds in U.K. Pat. No. 2146327. Thus, the term “heliochromic” compound is used in this specification to mean a compound which possesses the following properties, namely (a) a high quantum efficiency for coloring in the near ultra-violet, (b) a low quantum yield for bleaching with visible white light and (c) a fast thermal fade at ambient temperature but not so rapid that the combination of white light bleaching and thermal fade prevent coloring by the U.V. component of strong sunlight. Such properties make the compound eminently suitable for use in photoreactive lenses.
In U.K. Patent Applications Nos. 86/11837 and 87/050,101, there is described a series of pholochromic adamantane spiropyrans which possess the above-described desirable heliochromic properties, in conjunction with good thermal and photo-chemical stability. These adarlantane spiropyrans can also be incorporated into standard plastics lens materials, such as CR39 by imbibition and members of this series have been shown to be capable of undergoing a large number of cycles without significant degradation. It has been described that the reason why these compounds exhibit these improved properties is that in accordance with Bredt's rule, the spiro-carbon cannot become doubly-bonded and therefore the ring-opened colored form is resistant to degradations associated with 1,5-hydrogen shift.
However, one limitation of the compounds of this series is that the compounds which show the best resistance towards degradation exhibit a color change on exposure to a U.V. light (or sunlight) from colorless to yellow/orange. The market demand is, however, largely for lenses that darken to brown or gray. The above applications indicate that a photoreactive lens can be produced by incorporating a blend of a yellow and a blue photochromic compound into the lens. In practice, however, it has proved difficult to prepare purple/blue coloring photochromic compounds whose resistance to degradation or fatigue is equivalent to that of the best of the yellow coloring adamantine spiropyrans.
U.S. Pat. No. 4,818,096 describes photoreactive lenses with adamantine spiro compounds in which a mixture of photoreactive dyes is used to overcome the deficiencies of the individual dyes, In particular, this Patent describes the use of a combination of a) an admantine 2-spiro-benzopyran or 2-spiro-naphthopyran and b) a blue coloring photochromic benzopyran or naphthopyran having a nitrogen-containing substituent in the 2-position of the pyran ring. The combination of the yellow/orange coloring admantine 2-spiro pyran compound and the purple/blue coloring pyran provides a desired brown/gray coloration in the darkened areas. The blue coloring pyrans having the nitrogen-containing substituent in the 2-position are described a s novel where the 2-position substituent comprises a phenyl group having an amino or substituted amino or nitrogen-containing heterocylic substituent in the ortho-position or para-position of the phenyl group. These novel dyes were shown in the lenses only in combination with the yellow/orange coloring dyes. The invention touts the ability of the unique structure of the dye in providing a double maximum absorption from the dye, one absorbing at about 590 nm and the other absorbing at 500 nm and below to provide a purple/blue coloring pyran.
Various classes of photochromic compounds have been synthesized and suggested for use in applications in which a sunlight-induced reversible color change or darkening is desired. U.S. Pat. No. 3,567,605 (Becker) describes a series of pyran derivatives, including certain benzopyrams and naphthopyrans. These compounds are described as derivatives of chromene and are reported to undergo a color change, e.g., from colorless to yellow-orange, on irradiation by ultraviolet light at temperatures below about −30° C. Irradiation of the compounds with visible light or upon raising the temperature to above about 0° C. is reported to reverse the coloration to a colorless state.
U.S. Pat. No. 5,066,818 describes various 3,3-diaryl-3H-naphtho[2,1-b]pyrans as having desirable photochromic properties, i.e., high colorability and acceptable fade, for ophthalmic and other applications. Also disclosed by way of comparative example in this patent are the isomeric 2,2-diaryl-2H-naphtho[1,2-b]pyrans, which are reported to require unacceptably long periods of time to fade after activation.
U.S. Pat. No. 3,627,690 describes photochromic 2,2-di-substituted-2H-naphtho[1,2-b]pyran compositions containing minor amounts of either a base or weak-to-moderate strength acid. The addition of either an acid or base to the naphthopyran composition is reported to increase the fade rate of the colored naphthopyrans, thereby making them useful in eye protection applications such as sunglasses. It is reported therein further that the fade rate of 2H-naphtho-[1,2-o]pyrans without the aforementioned additives ranges from several hours to many days to reach complete reversion. U.S. Pat. No. 4,818,096 discloses purple/blue coloring photochromic benzo- or naphthopyrans having at the position alpha to the oxygen of the pyran ring a phenyl group having a nitrogen containing substituent in the ortho- or para- positions.
U.S. Pat. No. 5,888,432 describes that the presence of an adamantyl group in position 2 of naphtho- or benzopyrans allowed lowering the lambda-max of the colored form. These types of molecules adapt well in association with blue and/or violet and/or red complementary photochromes to give gray or brown tints. Those benzopyran derivatives are substituted in position 2 with an adamantyl group, itself optionally substituted with at least one linear or branched alkyl group that comprises from 1 to 6 carbon atoms. Advantageously, the adamantyl group is linked in position 1. The carbon in position 2 of the benzopyran derivatives (the carbon which carries therefore the adamantyl group and advantageously the adamant-1-yl group) is an asymmetric carbon. In the context that invention, the carbon, in position 2, in addition to the adamantyl group, bears a second substituent group S. These 2-adamantyl-2-S benzopyrans have particularly interesting photochromic properties.
U.S. Pat. No. 5,955,520 describes photochromic indeno-fused naphthopyrans in which an indeno ring group is fused to the f-side of the naphtha portion of a naphthopyran, and having specific substituents at the 3-position of the naphthopyran. A list of acceptable 3-position substituents for the practice of that invention is provided in detail on columns 3-5 of this patent reference, which patent is incorporated herein by reference for the totality of that disclosure. The data shows, for the very limited number of examples evaluated in Table II, the dyes with two λmax absorption peaks (e.g., Dye 1, λmax=425 (minor), 536 (major); and Dye CE1, λmax=407 (minor), 482 (major)).
In accordance with the invention of U.S. Pat. No. 5,955,520, certain novel 1H-indeno-2,1-f-naphtho[1,2-b]-pyrans having activated colors ranging from orange to blue/gray, an acceptable fade rate, high activated intensity and a high coloration rate may be prepared. These compounds may be described as indeno fused [1,2-b]-naphthopyrans having certain substituents at the 3 position of the pyran ring. Certain substituents may also be present at the number 5, 6, 7, 8, 9, 10, 11, 12, or 13 carbon atoms of the compounds
There is a continuing need for novel photoreactive or photochromic dyes and compositions that can provide different chromic and physical properties.